I recognize "今日" as "today/now", "は" as "is" and "暑" as "hot" (climate-wise). But I don't know what "かったからな" is, although "な" may mean "isn't it?". So it could be, "It sure is a hot day."
As for "私も汗をでしまった" I'm not sure. But if "今日は暑かったからな" is "It sure was hot today." then "私も汗をでしまった" might mean "I even broke into a sweat."
Because it was so hot today,I'm all covered in sweat, also.